Good questions MSJ! Had to do some thinking / reflecting. Longish post incoming

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Regarding what's contained within TNG, I'm guessing there will be nothing in terms of conclusions. Most like a series of interconnected short stories - largely a world building exercise.
If its 300 pages on atrocities, I doubt I'll finish it. But, just as TUC had just a few instances of that, I'm sure this one will too.
If its 'more of the same', ie if the story continues along the logical path that's been laid out from the start, I'll be satisfied. I don't know what that'll be, and I don't really
hope it'll be anything in particular, but that its consistent. I'll be upset if it does a 180 turn and all of a sudden its rainbows and butterflies.
Regarding "how much more can be said": Earwa is a massive universe. I'm sure Bakker could write stories within this world he intricately crafted for all the days of his life, and there would still be stories left untold. After all, its taken him nearly 30 years to tell just one story - the story of The No God. So what's left to be said? We've only just finished the prologue.
(To me, given the IRL time scale, its like asking "what's left" after reading Crippled God, or better yet since Erikson wrote the whole thing in about a dozen years, think of it as Bakker just got finished with House of Chains and it'll take him another 60 years to finish writing what's left of Earwa. Obviously TSA has been far more linear than MBOTF and the analogy is kind of weak and breaks down under scrutiny, but maybe that helps illustrate what I'm thiking?)
What interests you about TSA if not a chance at humankind pulling through?
There's little that's as subjective as what an individual likes, and I've got two answers for this specifically.
One, I enjoy the story, the universe, and the story telling. Something about it just gets me every time. I'm not sure I can precisely identify why, really. What makes TSA interesting is the world itself. All the ways everything is so intricately entangled. All the mysteries. The very human struggle to do, and to strive. To believe, and to live - the story really comes alive in parts for me, and I love it. So whatever stories Bakker writes about Earwa and beyond, I'll most likely read. For anyone new here - yes, I'm a fanboy lol.
But, two, what makes TSA interesting to me is that its
not about humanity pulling through.
All the failures. The islands of success amidst the endless sea of failure. Glimmers of hope, despite all the hardship. To me, think of it like the how Yatwer priestesses regard donations - it doesn't count if you do it to buy favor into heaven. The story itself loses its meaning if everything works out in the end. Its not courage if know you'll succeed. To that end, the story has accomplished that in many small ways. Whether the plot of TNG resolves and humanity wins out, I'll probably not be (too) upset, because of how hard fought that will have been. Despite whatever larger resolution, there was still Proyas and Saubon, Akka and Esmenet, all those that were lost and broken along the way. I don't want, or need, a greater resolution to make TSA a better story. It might cheapen everything for me a bit though. Re-reading it,
knowing that Proyas is betrayed makes his journey that much more heartbreaking. In the same way, if it does so happen that Bad happens (evil prevails, humanity dies, world is shut, etc. etc.), the story is more emotional for it. I get other's feel the opposite, and that's cool too

, but you had asked for my opinion, so there you have it.
TL;DR I'm a sucker and just like Bakker's writing. Earwa is cool too - I want more stories.